1. Field of the Invention
The present invention relates to a FET-based sensor for detecting an ionic material, a device for detecting an ionic material including the FET-based sensor and a method of detecting an ionic material using the device.
2. Description of the Related Art
Transistor-based biosensors are a kind of sensors detecting ionic materials, especially biomolecules, using electrical signals in aqueous solution. Transistor-based biosensors are manufactured through semiconductor manufacturing processes and have been significantly researched due to the advantages of high-speed signal transition and easy combination with an integrated circuit (“IC”) and micro-electro mechanical systems (“MEMS”).
U.S. Pat. No. 4,238,757 is a patent relating to the detection of a biological reaction using a field effect transistor (“FET”). This patent relates to a biosensor detecting an antigen-antibody reaction by measuring a current resulting from a change in surface charge concentration in a semiconductor inversion layer. The patent relates to the detection of a protein among biomolecules.
FET biosensors are cost and time efficient compared to conventional methods. In addition, FETs can be relatively easily integrated with IC and MEMS processes.
Probe biomolecules may or may not be fixed to a surface of a gate electrode of the FET-based biosensor. A method of detecting biomolecules using a FET-based biosensor includes measuring a change in current according to the binding of a target biomolecule to a surface of the gate electrode to which probe biomolecules may or may not be fixed. In an alternative method, a change in current according to the presence of a target biomolecule in a certain distance from a gate electrode to which no probe biomolecules are fixed can be measured.
An example of a conventional FET-based biosensor is a sensor including a single FET. Conventional FET-based biosensors, however, cannot separate signals derived from target biomolecules from noise, such as a drift signals spontaneously generated due to a reaction on a surface of a gate electrode, and signals generated due to the pressure of inflowing solution.
Japanese Patent Laid-open No. 2003-322633 discloses another example of a conventional FET-based biosensor including two FETs having different structures and electrical characteristics in a single chamber, wherein probe biomolecules are fixed to a surface of a gate of one of the FETs and the other FET is used as a reference FET.
However, since the two FETs of the biosensor use different surface materials, signals from the reference FET do not show drifting, which occurs in the sensing FET, and thus cannot be used for signal correction. Thus, the sensitivity of the biosensor is still low.